Acetaldehyde is a flavor chemical which imparts the impression of freshness to flavors in which it is used, particularly fruit flavors. In order for acetaldehyde to be used in instantized foods, it must first be encapsulated in a dry form which releases the acetaldehyde under the conditions of use. For economic reasons, the amount of acetaldehyde fixed in the encapsulate must be as high as possible. Amongst the current methods of encapsulating acetaldehyde, spray-drying and freeze-drying are the most successful means of achieving a high fix level of acetaldehyde. Generally, fix levels above 2% are adequate, but 9 to 12% are preferable. The present methods for spray-drying acetaldehyde suffer from three disadvantages:
1. Acetaldehyde boils at 21.degree. C. Spray-drying temperatures are usually in the range of 150.degree.-200.degree. C., consequently, large amounts of acetaldehyde are lost to evaporation during the spray-drying process. Losses can be as high as 90%. PA1 2. Acetaldehyde has a flash point of -40.degree. C.; therefore; normal spray-drying temperatures make this a potentially hazardous process. PA1 Maltrin-100; PA1 MOREX.RTM.; PA1 LODEX.RTM.; PA1 Gum Acacia; PA1 Gum Arabic; PA1 Xanthan Gum; and PA1 Guar Gum.
3. Spray-drying acetaldehyde can give a product with varying amounts of two undesirable contaminants which arise from the reaction of acetaldehyde with itself. These contaminants are crotonaldehyde and paraldehyde.
Freeze-drying, on the other hand, is accomplished at temperatures well below 0.degree. C.; consequently, losses of acetaldehyde due to evaporation are lower than for spray-drying. Because of the low process temperatures, freeze-drying acetaldehyde is a safer process than spray-drying. However, the present state-of-the-art freeze-drying produces varying amounts of the same two undesirable contaminants found in acetaldehyde which has been spray-dried (crotonaldehyde and paraldehyde). In the case of freeze-dried acetaldehyde, the level of paraldehyde is far greater than spray-dried material. This results from the chemistry of formation for the paraldehyde. At temperatures below 12.degree. C., paraldehyde crystallizes out of solution. This drives the trimerization reaction of acetaldehyde to paraldehyde.
The present disclosure is for a process of freeze-drying acetaldehyde which obviates the disadvantages of existing state-of-the-art encapsulating methods.